Up to 2 radio receivers from the FS20 system can be triggered with the 2-channel door/window contact FS20 TFK according to criteria which can be set separately. It adopts the contact opening & closing message for 2 internal reed contacts which are triggered by a magnet, or externally connectable contacts. These contacts can monitors doors & windows or other flaps, drawers, locks, step & make contacts. The reed contacts can be triggered either on the left or right by the FS20 TFK, so that the device can be used very universally.